Ephemeral messaging refers to arrangements whereby one user sends a message such as a picture message to a destination user, typically over the Internet, and the message is only allowed to be temporarily available on the destination user's terminal. I.e. the receiving instance of the ephemeral messaging application is configured to automatically delete the message after a certain amount of time has elapsed since the message was received, perhaps only a few seconds. The purpose of this is privacy, so that the destination user cannot continue to view the message indefinitely, or redistribute the message against the sending user's will.
Voice mail services such as commonly provided in mobile cellular networks also automatically delete messages, but still only based on the amount of time elapsed since each message was received. I.e. a user (the callee) has access to a mailbox which is able to record and store a voicemail from the caller whenever the callee misses a callee, and the messages remains available to the callee to access for a certain number of days or weeks, after which the service automatically deletes the message. The purpose here is to stop the inbox becoming cluttered with an unwieldy number of messages.
In one previously proposed scheme that is somewhat different to ephemeral messaging applications and voicemail services, messages are received at a pager and are stored in a finite number of message slots corresponding to the pager's maximum storage capacity, and the messages are deleted not after a predetermined time has elapsed, but rather once the total number of messages has reached the maximum possible number of message slots. I.e. if a new message is received and the total number of messages has already reached the maximum, an existing message is deleted to accommodate the new message. If there are both read and unread messages in the slots, read messages are deleted in preference to unread messages. The scheme was proposed in the early 1990s when portable user devices had a very limited storage capacity, even for very simple textual messages, but as storage capacities of user devices rapidly accelerated the scheme has apparently lost relevance and is not seen in modern devices, as far as the authors of the present application are aware.